Calculate IPv4 network address and CIDR mask from IP address (dotted quad) and network mask (dotted quad)

ip_and_netmask2cidr.sh

# $1 is a decimal number between 0-255
dec2bin () {
    [ -z "$1" ] && return
    D2B=({0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1})
    echo ${D2B[$1]}
}

# $1 is ip address (dotted quad)
# $2 is netmask (dotted quad)
calc_network () {
    [ -z "$1" ] && return
    [ -z "$2" ] && return
    IFS=. read -r i1 i2 i3 i4 <<< "$1"
    IFS=. read -r m1 m2 m3 m4 <<< "$2"
    full_mask_bin="$(dec2bin $m1 )$(dec2bin $m2 )$(dec2bin $m3)$(dec2bin $m4)"
    mask_bin=$(sed -r 's/0*$//' <<< "$full_mask_bin")
    printf "%d.%d.%d.%d/%s\n" \
           "$((i1 & m1))" \
           "$((i2 & m2))" \
           "$((i3 & m3))" \
           "$((i4 & m4))" \
           ${#mask_bin}
}